In order to achieve more efficient usage of electric power, it is desirable to monitor operation states (operation statuses) of the individual electrical appliances. Such monitoring could be realized by attaching a sensor to each electrical appliance. This enables measuring operation statues (operational and non-operational statuses, and electric power consumption) of each electrical appliance, thereby making good use for electric energy conservation, electric power supply control and others by perceiving the operation statues of the electrical appliances based on the results measured by the sensors.
Attachment of a sensor to each of the electrical appliances, however, increases the number of sensors, which increases additional costs for attaching the sensors and constructing a system, such as a wireless one, to collect measurement signals outputted from the sensors, which is unavoidable from becoming high costs.
In order to solve such a problem, some technologies have been developed to make it possible to monitor the operation status of each electrical appliance without installing any sensor on each of the electrical appliances so that a monitoring device can be used in a household and the likes at a low cost.
Such a conventional individual electrical-appliance operation-status estimation device and a conventional method are disclosed in a patent document 1 shown below.
The individual electrical-appliance operation-status estimation device described in patent reference 1 implements Non-Instructive Appliance Load Monitoring (NIALM) that measures electric power usage and operation characteristics of each electrical appliances by using pattern recognition of pulse-type waveforms based of the electric characteristics of the total electric power usage of the operating electrical appliances.
That is, concretely, the prior individual electrical-appliance operation-status estimation device measures the electric characteristics (admittance consisting of conductance and susceptance) of total load of the electric circuits connected with equipment in a household, thereby generating analog signals proportional to the electric characteristics. The device includes sensing means, an AD convertor, and a signal processing means. The sensing means employs a voltmeter and an ammeter that are connected with the electric circuits at positions apart from the equipment. The AD convertor converts the analog signals into digital signals. The signal processor divides the total load of a plurality of units into parts corresponding to the respective units according to the digital signals.
Incidentally, using the above-described processed results, the operation statutes of electrical appliances are capable of being individually shown on a display.